1. Field of the Invention
The present invention relates in general to a machine tool and more particularly to a pallet changer for selectively transferring workpiece set up pallets onto and from a work table of the machine tool.
2. Description of the Prior Art
Heretofore, there has been used a pallet loading and unloading device for exclusive use in loading a workpiece set up pallet onto a work table and unloading it from the table of a machine tool. The work table is provided thereon with a pallet clamper for guiding the pallet during loading and unloading operations as well as for clamping it on the work table. The clamper is connected with a piston of a clamping cylinder device which is disposed at the center portion of the work table. The clamper, when in a lifted-up position for unclamping the pallet in advance of loading and unloading operations, is brought into support only at its center position, and its opposite end portions in a pallet transfer direction are brought into an overhung situation without support.
For this reason, at the time of loading and unloading operations when the weight of the pallet mass and a workpiece set up thereon is loaded on one of the opposite end portions of the clamper without support, then the clamper is deformed to have a level different from that of a pallet rest of the loading and unloading device. The heavier the weight of a pallet and a workpiece handled in such a machine tool the greater the problems created. Accordingly, difficulties may occur when the pallet is transferred between the work table and the pallet rest.